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CELLS
•the basic unit of life
•living things are composed of at least one cell
•cells metabolize (obtain energy, use energy, make waste)
•cells can reproduce
•cells sense and respond to the environment
red blood cell
brain cell
sperm
Some human cells
egg
• Cells need large surface area to volume
ratio
3 parts of eukaryotic cell
Cheek epithelial cells
1. plasma (cell) membrane
“Selectively permeable”
Lipid bilayer
hydrophilic outer/inner portions
hydrophobic within
The membrane determines what can get
into and out of the cell such as……..
Fluid mosaic model
Dynamic!
3 types of membrane proteins
1. Receptors bind substances
Example: insulin receptor
2. Enzymes Catalyze (speed up) reactions
Example: lactase
3. Transporters, Channels ferry
substances
Example: chloride ion channel
Cystic fibrosis (CF)
• most common serious genetic disease in the US
• A single gene mutation causes a cell membrane
Cl- transport protein to malfuncton
Cells produce thick, sticky mucus that clogs
the lungs  infections
2. DNA
• Eukaryotic cells have a nucleus that contains
DNA
• Why is DNA important?
DNA in
nucleus
• DNA = instructions for cells to
manufacture proteins
• DNA = genetic material
• DNA is in the form of chromosomes
46 long strands of DNA per cell
(23 in egg and sperm)
3. cytoplasm (fluid-like interior)
– Contains ORGANELLES
2 Organelles found in cytoplasm of
eukaryotic cell
1. lysosomes
– Bags of enzymes that clean old parts,
digest foreign matter
Tay Sach’s disease
• Mutation in a single gene results in a malfunctioning
lysosomal enzyme
• Lysosomes fill up with lipid (fatty substance)
• Normal until ~ 1year, brain deteriorates, fatal ~age 3
Microscopic view of affected
brain
Cherry spot on eyeball
Lysosomes and apoptosis
• Apoptosis = programmed cell death
• Ex. Tadpole tail, fingers during human
embryonic development
Tarahumara Frog (Rana tarahumarae)
•
•
Syndactyly 1/2000 births
Disappears at 4 months gestation
Between 50 billion and 70 billion cells die
each day due to apoptosis in the average
human adult. In a year, this amounts to the
proliferation and subsequent destruction of
a mass of cells equal to an individual's body
weight.
2. mitochondria
– produce energy (ATP)
– use oxygen and fuel
(sugar)
Chapter 10
The human life cycle
DNA has the instructions
• These instructions are on chromosomes
which contain units of information called
genes
Gregor Mendel (~1850) the “father
of genetics”
Worked out the transmission of traits from parent to
offspring using pea plants
What makes peas good
genetic subjects (compared
to humans)?
• Pisum sativum
• Single gene traits
Distinct pea plant traits
•
•
•
•
Start with true-breeding varieties
Cross or self pollination
Keep detailed records
Statistical analysis
1. Particulate theory of inheritance
• Modern version: Genes are physical units
passed from parent to offspring
The monohybrid (one gene) cross
2. Principle of dominance : For each gene
we have 2 alleles
Dominant allele – observed in
phenotype (appearance)
B = brown eye allele
G = yellow pea allele
recessive allele is masked by a dominant
allele
b = blue eye allele
g = green pea allele
BUT, each individual has two
alleles per gene. What are the 3
possible GENOTYPES?
3. Principle of segregation
• Modern version: each sperm and egg
randomly gets one allele per trait and
fertilization gives the new individual 2
alleles per trait
Sickle cell disease
S = normal allele
s = sickle cell allele
Mutation in the gene for
hemoglobin
Red blood cells form a sickle
shape when oxygen is low
• The sickled red blood cells cannot fit
through capillaries
Causes joint pain, anemia –
why?
Over time stresses kidneys,
heart, other organs
An example of pleiotropy = single gene, multiple
effects
Other one gene traits
P-
W-
S-
A-
Just because it’s
dominant doesn’t mean
most people have it
D-
C-
Albinism (aa)
• All people have harmful recessive genes
BUT the likelihood that you will mate with
another person who has the same allele is
low
Infantile Neuroaxonal Dystrophy (NAD
Review of other genetic traits
Marfan’s disease and pleiotropy fig. 10.13
Continuous variation results from
many genes (polygenic)
Examples:
Bell shaped curve shows
continuous variation
IQ is polygenic
phenotype also affected by
environment
-Skin color
melanin production
increased by sun
-Height is ~90% genetic
Chapter 13
Chromosomes = strands of DNA in
nucleus
Gene = unit of
information on a
chromosome
DNA = molecule that
composes
chromosomes/genes
Genes (and alleles) are located on
chromosomes
Humans have ? #chromosomes
in each somatic cell nucleus
Somatic cell = body cell
(not sperm or egg)
A human chromosome in nucleus
Chromosomes are copied before a cell
divides into 2 cells so that each new cell
has a full set
chromosome
Note the coiled, thread-like
structure
Humans have 2 sets of
chromosomes in each cell
• 23 from egg
• 23 from sperm
n
Homologous chromosomes
Chromosomes of (most) animals are in pairs
Homologues have same genes at same positions
Each chromosome
has 100s or 1000s
of genes
alleles at gene position may be
different
Your combination of alleles
is unique to you!
Chromosomes and genetics
Human
Chimpanzee
Dog
Cat
Alligator
Goldfish
Mosquito
Potato
Baker’s yeast
46
48
78
72
32
94
6
48
34
The more complex the organism the more
chromosomes??
Karyotype – photo of chromosomes
arranged according to ?
Pairs 1 through 22 =
autosomes
Sex chromosomes are X
and Y
Note the homologous pairs
Cant see individual genes!
Fig. 10.14
•Autosomes are the
same in male and
female
•The Y chromosome
determines sex!
•What genes are on the
Y? The X?
Chromosomal number disorders
47, XX, 21+
Down syndrome
Page 136 (ch 9)
Klinefelter syndrome
• Chromosomal notation?
Chromosomal changes
Translocation = piece of one chromosome  another
*C. Deletion –small piece of a
chromosome lost
• Example: Cri du Chat (pg. 198)
High-pitched cry (identified as a cat-like cry)
Low weight
Poor muscle tone (hypotonia)
Microcephaly (small head size)
Micrognathis (small jaw)
Hypertelorism (wide spaced eyes)
Round face
Low set ears
Feeding difficulties
Delays in walking
Scoliosis
Language difficulties
Mental retardation
Organ defects
1/50,000 live births
D. Inversion – a piece of a
chromosome inverts (flips)
16 year old with
leukemia (AML)
Note – this
karyotype is
from the
cancerous cells
only
Cartoon of cytogenetics UWISC
Genetic testing
1. Of children and adults
– Obtain chromosomes/DNA from cells for
testing
2. Prenatal testing
• 1. ultrasound – for fetal anatomy, age,
size, twins
– Can pick up defects such as spina bifida
2. Fetal testing
Test fetus in utero
A. amniocentesis
Obtain fluid from sac via needle through uterus contains fetal cells
Slight risk of miscarriage, perform ~ week 14
 Karyotype or gene test
B. Chorionic villus sampling
• Tube through vagina
into uterus
• Obtain cells from
placenta
• Greater risk of
miscarriage
• Done at ~week 5
3. Embryo testing
In vitro fertilization (IVF) > Remove one cell from
an early embryo
> why?
Implant embryo in uterus
Ethical implications of embryo
testing
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Could choose gender of child – is this right?
Could people test for other traits too?
Will this lead to eugenics?
Health insurance doesn’t pay for IVF (usually) or embryo
testing – who can afford it?
How is are the testing centers regulated?
Prenatal testing may (does) lead to abortions (even if
disorder is not fatal as in Down syndrome)
Improves odds of having a healthy baby
Could be ready to treat a baby or be emotionally
prepared
Genetic profiling
What type of genes would
you like to know about?
Predisposition genes
– Predict health risk for:
• Diabetes, cancer, Alzheimer, etc…
• Metabolic profile
– How a person “handles” a drug
Ethical implications of genetic profiling
• Voluntary or required?
• Insurance companies or employers have your
data
– Could “scavenger hunt” for predisposition genes
• Alcoholism, cancer, alzheimer’s
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Who can afford the tests?
Counseling needed
Is it a good thing to know the future?
May influence whether or not to have children